The following correction was printed in the Guardian's Corrections and clarifications column, Tuesday 21 July 2009

The piece below on Martha Reeves mentioned the elation of Martha and the Vandellas at playing Memphis – "Elvis Presley's hometown" – in a Motortown Revue tour in the early 1960s. To clarify: Presley lived mainly in Tennessee's largest city from the age of 13; he was born and raised 100 miles down the road in Tupelo, Mississippi.

During the summer of 1965, an epoch-defining precursor to the pop video was shown on US television. In it, Martha Reeves and the Vandellas, one of Motown's most successful singing groups whose hits include Jimmy Mack and Dancing in the Street, skip like unruly schoolgirls along a Ford car production line in Detroit. Followed by her two backing singers, Reeves hops in the back of a half-assembled Mustang - the vehicular symbol of rebellious youth at the time - and all three continue singing Nowhere to Run as the car glides forwards and a gleaming engine is lowered on to the chassis.

The founder of Motown, Berry Gordy, had based his business model on the Ford assembly line on which he had once worked, and according to Reeves, the resulting "pace, urgency and pressure" of the recording process was precisely what allowed her to deliver the song with such oomph.

The company is currently celebrating its 50th year and, this week, Reeves, now 67, is touring the UK with fellow Motown veterans such as the Commodores, the Miracles and Mary Wilson of the Supremes. Perched on a flouncy sofa in a London hotel, resplendent in a black leather maxi-skirt and ample gold jewellery, she reminisces about growing up in Detroit.

"There was always music in my house. I'm from a large family [of 11 children] in the generation before television, so we did a lot of listening to the radio and singing of gospel songs, with my grandfather being a Methodist minister. And my dad played guitar and sang the blues like nobody."

Reeves was born in Alabama and, although her family moved north to Detroit soon after, there is more than a whisper of southern drawl to her voice. When, aged 20, she first clapped eyes on Motown's original Detroit headquarters, it was little more than a cottage industry. "I got off the bus and saw this house, with its hand-painted 'Hitsville USA' sign, and almost went home again," she recalls. Motown's head of A&R, William Stevenson, had handed her his card after hearing her sing at the 20 Grand, a nightclub in the then-booming city. Reeves promptly quit her day job as a cleaner and showed up at Hitsville the very next morning.

Part of Gordy's grand plan had been for his black soul singers to appeal to multi-racial audiences, and he famously put his rising stars through "artist development" classes. This gave them, as Reeves puts it, "a certain poise, class and Motown signature. We went in saying, 'We just want a hit record, we don't care nuthin' 'bout singing for kings and queens and lords and ladies.' But," she says, "I can now say we've all had royalty in our audience." Their Motown tutors, Reeves says with heartbreaking sincerity, "made us socially acceptable."

Reeves wrote in her autobiography that, ahead of the very first Motor City Revue tour, in 1962, "Berry gave us a great pep talk: 'You're not only representing Motown Records,' he said, 'you're representing all of Detroit.' As the bus pulled away, real tears were falling."

The women had been assigned a chaperone who lectured them about the risks of "becoming intimate" with boys. "Everywhere you went you had somebody trying to take advantage of you," says Reeves, frowning. Is it true that many of the Motown ladies had crushes on Marvin Gaye? "Well, we all loved Marvin," she shrugs.

As the Motor City Revue travelled south, Reeves witnessed segregation like she had never seen before. When they pulled into a petrol station in Birmingham, Alabama - a hotbed of civil rights activity - they were chased away by an old white man wielding a shotgun, calling them niggers. And when they played Memphis, their elation at being in Elvis Presley's hometown was quickly dampened by the sight of their racially split audience - whites on one side, blacks on the other.

Although segregation was illegal in Detroit, the city was no stranger to racial tension. When the "big three" automobile companies (Ford, Chrysler and General Motors) moved to new plants in the white-only suburbs, they left behind them a yawning ghetto with few jobs for the black population. On a sweltering day in July 1967, a police raid on a speakeasy ignited race riots that left 43 dead and more than 2,000 buildings burned out.

"It was gonna happen," says Reeves. "There was enough racial insult and bias, and pain on our people because of their colour. We knew that there was gonna be a riot, we just knew that."

Reeves was on stage when the riot broke out. "We were about to sing Jimmy Mack when someone told me: 'Let everybody know they must leave the theatre, cos there's a riot and a curfew, and they gotta get home before eight o'clock. And do it calmly because you'll cause a stampede." The following day, the Vandellas were due to go on tour. "We had to go to the airport early in the morning, and the city was burning," she says, devastated all over again.

When the tour rolled into New Jersey, another riot started. "We were scared out of our minds and so far from home," says Reeves. "We were holed up in a hotel for four days. Radio DJs would call us on the phone and have us talk to the public. We'd ask them to try not to burn anything down ... to stay in their homes and not join the riotous gangs."

Nowadays, Reeves spends more time in an office than a tour bus, as an elected member of the Detroit city council. Why the switch to politics? "My business slowed down. People haven't deserted our music, but they kinda put us in a place where music goes when it gets to be of some age. And I felt that I could be of help to the city of Detroit." With the American car industry on the brink of collapse, 30% of its population living below the poverty line and 1,000 residents deserting it every month, the city needs all the help it can get.

Reeves is determined that it is not too late to save her beloved Motor City. "We've got the alternative fuel plants, two already set up. And different car manufacturers are making the electric car." She puffs with pride as she raves about how "fabulous our downtown is now".

Her son still lives in Detroit too - he works for Chrysler and his wife for General Motors. "They have given me a 20-year-old granddaughter who is at university. My grandson, Eric Jr, has graduateed from high school, and Elijah's 10, so I'm happy."

Does she feel that Barack Obama's presidency offers some sort of conclusion to the racial tension that has been present throughout her life? "It was a unanimous decision across all races and creeds and colours, and I think we'll have a better United States now he is our elected president." Has she met him? "Yes I have, on three occasions. He's quite a gentleman - a very charming man and very intelligent. He reminds me a lot of Marvin Gaye."